Physiological and Photosynthetic Characteristics of Pumpkin Seedlings Cultivated Under Low-Light Stress

Low-light stress is known to have a significant impact on pumpkin yield in greenhouse conditions, it is crucial to understand the characteristics of low-light tolerance and identify resistant germplasm resources. In this study, four pumpkins (Cucurbita moschata) varieties were used, including three inbred lines (10-32, NY-1, and JB-1) and one hybrid line (NY-1 x JB-1). Various low-light treatments (T0, no shade; T40, 40% shading; T80, 80% shading) were set, to explore their effects on morphol-ogy, photosynthetic characteristics, osmotic regulation substance content, and antioxidant enzyme activity in pumpkin seedling leaves. In the results, seedlings of inbred lines 10-32 and JB-1, as well as hybrid NY-1 x JB-1, exhibited low-light resistance with shading rate increases. The maximum photochemical quantum yield of photosystem II (Fv/Fm) of all varieties decreased under low-light stress. Catalase (CAT) activity initially increased and then decreased, while superoxide dismutase (SOD) activity showed the opposite trend. Peroxidase (POD) activity gradually increased in 10-32, JB-1, and NY-1 x JB-1, with JB-1 showing a significant increase at T80, and NY-1 displaying an initial decrease followed by an increase. Noteablely, the soluble proline (Pro) content decreased IP: 203.8.109.20 On: Tue, 05 Dec 2023 13:24:23 in 10-32, NY-1, and NY-1 x JB-1. Significant differences in malondialdehyde (MDA) content were Copyright: American Scientific Publishers observed among the seedlings of four varietis. The MDA contents increased in 10-32 and JB-1 Delivered by Ingenta under T0 and T40, while showed no significant change in NY-1. The MDA content at T80 significantly decreased in NY-1, and first decreased and then significantly increased in NY-1 x B-1. The soluble sugar content in 10-32 remained unchanged between T0 and T40, but significantly increased at T80. While in JB-1 and NY-1, it initially increased then decreased with increasing shading rate. The trend in NY-1 x JB-1 was opposite to that of JB-1 and NY-1, with initially decreased followed by a significant increase. In conclusion, morphological characteristics associated with low-light tolerance can serve as reference indices for breeding low-light tolerance pumpkins. These parameters can be used as reference indices to assess pumpkin resistance to low-light stress.